fix: pass file name to unstructured-api (langchain-ai#742)

fix langchain-ai#738

Reference link

examples/src/document_loaders/example_data/notion.md

@@ -0,0 +1,41 @@
+# Testing the notion markdownloader
+
+# 🦜️🔗 LangChain.js
+
+⚡ Building applications with LLMs through composability ⚡
+
+**Production Support:** As you move your LangChains into production, we'd love to offer more comprehensive support.
+Please fill out [this form](https://forms.gle/57d8AmXBYp8PP8tZA) and we'll set up a dedicated support Slack channel.
+
+## Quick Install
+
+`yarn add langchain`
+
+```typescript
+import { OpenAI } from "langchain/llms/openai";
+```
+
+## 🤔 What is this?
+
+Large language models (LLMs) are emerging as a transformative technology, enabling
+developers to build applications that they previously could not.
+But using these LLMs in isolation is often not enough to
+create a truly powerful app - the real power comes when you can combine them with other sources of computation or knowledge.
+
+This library is aimed at assisting in the development of those types of applications.
+
+## Relationship with Python LangChain
+
+This is built to integrate as seamlessly as possible with the [LangChain Python package](https://github.com/hwchase17/langchain). Specifically, this means all objects (prompts, LLMs, chains, etc) are designed in a way where they can be serialized and shared between languages.
+
+The [LangChainHub](https://github.com/hwchase17/langchain-hub) is a central place for the serialized versions of these prompts, chains, and agents.
+
+## 📖 Documentation
+
+For full documentation of prompts, chains, agents and more, please see [here](https://hwchase17.github.io/langchainjs/docs/overview).
+
+## 💁 Contributing
+
+As an open source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infra, or better documentation.
+
+Check out [our contributing guidelines](CONTRIBUTING.md) for instructions on how to contribute.

examples/src/document_loaders/unstructured.ts

@@ -3,7 +3,7 @@ import { UnstructuredLoader } from "langchain/document_loaders/fs/unstructured";
 export const run = async () => {
   const loader = new UnstructuredLoader(
     "http://localhost:8000/general/v0/general",
-    "langchain/src/document_loaders/tests/example_data/example.txt"
+    "src/document_loaders/example_data/notion.md"
   );
   const docs = await loader.load();
   console.log({ docs });

langchain/src/document_loaders/fs/unstructured.ts

@@ -1,3 +1,5 @@
+import type { basename as BasenameT } from "node:path";
+import type { readFile as ReaFileT } from "node:fs/promises";
 import { getEnv } from "../../util/env.js";
 import { Document } from "../../document.js";
 import { BaseDocumentLoader } from "../base.js";
@@ -20,15 +22,16 @@ export class UnstructuredLoader extends BaseDocumentLoader {
   }
 
   async _partition() {
-    const { readFile } = await this.imports();
+    const { readFile, basename } = await this.imports();
 
     const buffer = await readFile(this.filePath);
+    const fileName = basename(this.filePath);
 
     // I'm aware this reads the file into memory first, but we have lots of work
     // to do on then consuming Documents in a streaming fashion anyway, so not
     // worried about this for now.
     const formData = new FormData();
-    formData.append("files", new Blob([buffer]));
+    formData.append("files", new Blob([buffer]), fileName);
 
     const response = await fetch(this.webPath, {
       method: "POST",
@@ -73,11 +76,13 @@ export class UnstructuredLoader extends BaseDocumentLoader {
   }
 
   async imports(): Promise<{
-    readFile: typeof import("node:fs/promises")["readFile"];
+    readFile: typeof ReaFileT;
+    basename: typeof BasenameT;
   }> {
     try {
       const { readFile } = await import("node:fs/promises");
-      return { readFile };
+      const { basename } = await import("node:path");
+      return { readFile, basename };
     } catch (e) {
       console.error(e);
       throw new Error(